I just got home from a party at which I talked with a guy who worked on an assembly line at a U.S. car manufacturing plant.
This is as close a paraphrase of the essence of what he said as I can remember:
"Quality control is a joke...We smoked dope a lot... Our welds were okay--usually. (He laughed.) My cars didn't squeak--usually. (He laughed.)... And we'd put coke cans and dead rats into the axle to see if QC (quality control) would find it. They never did." (He laughed.)